This book forms part of the "opus tripartitum" (including a gradual [1536] and a noted ferial psalter [1537] , that the Cologne printer Hero Alopecius (Fuchs) produced for the diocese of Münster after the Anabaptists had destroyed many liturgical books in the city during their "kingdom of a thousand years" in 1534-35. It is a rich source of historia with plainchant texts and melodies that are unique, or nearly unique, to antiphoners and noted breviaries written for use in the diocese of Münster. In addition to the office for St Liudger (Analecta Hymnica [AH] 26, no. 91), the first bishop of the diocese, one can single out the offices for St. Patroclus (not in AH), the Conversion of St. Paul (AH 28, no. 43), the Sending Forth of the Apostles (AH 5, no. 22), the Translation of the Three Kings (AH 5, no. 23), the Beheading of John the Baptist (AH 26, no. 51), Sts. Chrysanthus and Daria (AH 25, no. 73) and the Holy Lance (partly in AH 5, no. 7). All of these offices are part of a work in progress at the University of Cape Town that will include critical editions of the texts and melodies.

The differentiae of each mode have been numbered with a two-digit system: an upper-case letter indicating the final pitch of the differentia and a sequentially ordered numeral. The codes for differentiae and chants not found in CAO will be retained for the manuscript sources from the diocese of Münster that are currently being indexed.

Two breviary manuscript sources, containing the cathedral liturgy of Münster, were consulted in order to clarify Feast Name, Office and Position entries in the index for which the printed Antiphoner provides unclear or insufficient information: Münster, Nordrhein-Westfälisches Staatsarchiv, Verein für Geschichte und Altertumskunde Westfalens, Abt. Münster, Msc. 97 and Msc. 273 (D-MÜsa MSS AV97 and AV273). The Fraterherren of Münster wrote both of these volumes: the former (1464), containing the winter and spring parts, was written for Hermann von Langen, Dean of the Münster cathedral, while the latter (ca. 1480), containing the summer and winter parts was written for a canon of the same cathedral.